Vitamin A deficiency in rats results in striking decreases in the amounts of lipofuscin that accumulate in the retinal pigment epithelium, as a result of either normal aging or of vitamin E deficiency. The possibility of a dose-related response was tested by feeding rats diets either adequate (+E) or deficient (-E) in vitamin E and containing very different levels of vitamin A. The +E/high and -E/high A rats received 23.0 mg retinol/kg diet; the +E/low A and -E/low A rats received 0.23 mg retinol/kg diet; the +E/doubly low A and -E/doubly low A rats received .058 mg retinol/kg diet; and the +E/-A and -E/-A rats received no retinol. After 18 weeks and 30 weeks on the diets, the retinal pigment epithelial cells of all the vitamin E-deficient rats exhibited as many as fivefold more lipofuscin granules in sections examined by electron microscopy and did those of the vitamin E-adequate rats which received the same amount of vitamin A. Within the vitamin E diet groups, the rats receiving increasing amounts of dietary vitamin A had increasingly more lipofuscin in their retinal pigment epithelium. This apparent dose-related response suggests a close relationship between dietary vitamin A and lipofuscin formation.